What is a Passivhaus?

If you are like me, you have probably become very energy conscious. Conscious about the increasing cost, conscious about the environmental impact of obtaining energy and using it and conscious of not being able to afford to use it, full stop.

It was interesting to note that British Gas recently reported a fall in fuel demand for last winter. They attributed this to a mild winter. I do not recall the winter as being particularly mild. Rather it being not as cold as some. Winter is generally cold.

I doubt I am alone when I really do have to consider very carefully when, or indeed, if, I turn on the central heating at all.

Current energy policy in the UK seems to focus on supplying a potential for increasing energy consumption through investment in renewables and the development of controversial energy techniques such as fracking.

Increasing domestic energy costs to fund the development of intermittent energy sources and the exploitation of ever-diminishing fossil fuel reserves, may have the undesirable effect of reducing domestic energy consumption.

This causes untold misery for countless households that have little alternative other than to live in buildings that, by design, are not particularly energy efficient. Even new homes that are being built today and marketed as zero carbon are still significantly less energy efficient than a Passivehause.

A Passivehause, or passive house, uses innovate design and building materials to minimise energy consumption, reducing it to almost negligible levels whilst maintaining enhanced comfort levels within the building.

First developed in Germany in the 1990′s, a Passivehause works with its environment rather than imposing upon it. The building is specifically designed to be rigorously energy efficient. This allows it to conserve heat rather than relying on a constant supply of energy to maintain a comfortable living environment.

Building a Passivehause requires a complete shift in the current and traditional approach to building design and construction methods. Each passivehause must be individually designed from the ground up, and it must also take into account its location and the surrounding environment.

Using intelligent design in conjunction with a specialised computer software package, The Passive Hause Planning Package (PHPP), building designers and architects can fine-tune their designs.

Imputing various characteristics into the programme helps the designer to manipulate and modify the structure to maximise the energy efficiency of the building.

Although there are no set standards that must be adhered to, a Passivehause relies on a set of voluntary performance standards that accommodate many different ways of meeting the criteria for the Passivehause classification.

The design of the building requires that no thermal bridges are present in the construction. Thermal bridges conduct internal temperatures to the external environment and vice-versa.

Window construction must be of a superior design, typically triple glazed, filled with argon or krypton gas and the frames bonded into specialised insulation material to prevent heat transfer. The windows must provide a U-value of less than 0.8.

The building has to be encased in a quality insulation material, usually 300mm thickness and the building must be built to create an airtight internal environment. Some specialist insulation materials contain internal air pockets that enhance the insulation capabilities.

The building must optimise the heat from the sun and retain it along with heat generated by the activities of the occupants.

Ventilation is provided through a manual ventilation heat recovery system (MVHR) which must reclaim a minimum of 80% of the heat from extracted air and transfer that heat back to incoming air via the heat exchanger.

In order to meet the standards required for a building to be classed as a Passivehause, the heating requirement of the building must not exceed 15kWh/m/yr. In comparison, the maximum heat requirement set for a zero carbon new home for 2016 is 46kWh/m/yr.

The air changes in a Pasivehause must not exceed 0.6 times the entire house volume in one hour.

Consequently, the complete heat requirement of a Passivehause can be met by a small space heater supplied by a ground source heat pump and supplemented by solar energy. However, supplementary heat can be provided by gas boilers so long as the maximum kWh requirements are not exceeded.

Of course, each building will have different requirements dependent on the position of the building and the environment in which it is built. Building a Pasivehause at a latitude above the 60 line (London 51L) will increase costs due to greater insulation requirements and added design features such as underground heat storage facilities. This underground facility can reverse the conventional ground source heat pump technology to conserve summer heat for winter usage and vice-versa.

In general, the basic design and building costs are increased by at least 10% above conventional building costs. However, considerably more time is spent in the design process than current buildings require. Construction time is often minimised by the utilisation of pre-fabricated components.

Perhaps one of the most interesting facets of a Passivehause is the required change in the of the behaviour of the occupants. Any desire to open windows, such as for sleeping at night time has to be removed.

Once built, a Passivehause cannot be modified by expanding it, or by building extensions to it. Even fitting a satellite dish would seriously interfere with the structure by creating a thermal bridge. The occupants need to treat the building as a machine and co-exist with it.

Although not a particularly practical idea from a construction and financial position, it is possible to achieve Passivehause status in the renovation of an existing property, but in general, it is more economical to plan and develop one from scratch.

Nevertheless, as an alternative solution to energy concerns, a Passivehause construction produces superior comfort living environments for occupants at miserly energy consumption levels.

Passivehause status can be confirmed and certified by the Passivehause Institute following subjecting the property to a number of tests, but in practice, few Passivehause owners require that confirmation.

The principles utilised in domestic Passivehause construction can also be transferred into the design and construction of industrial facilities.

Great news for energy consumers, bad news for energy suppliers and governments.